Gasoline product

ABSTRACT

Aromatic blendstocks suitable for use in making an unleaded gasoline fuel for combustion in a spark ignition engine contain substantial amounts of diisopropylbenzene which provides relatively more energy for doing work while producing fewer carbon dioxide emissions as compared to current gasoline blendstocks. Unleaded gasolines made utilizing the foregoing aromatic blendstocks contain at least about 0.3 weight percent diisopropylbenzene, preferably about 0.3 to about 10 weight percent diisopropylbenzene.

FIELD OF INVENTION

[0001] This invention relates to automotive gasoline and blending stockstherefor.

BACKGROUND OF INVENTION

[0002] When gasoline products are formulated, it is done by mixingvarious petroleum blending stocks. Different blending stocks havedifferent properties known to refiners, and the properties of aparticular gasoline product can be modified by varying the relativeamounts of the different petroleum blending stocks that together make upthe gasoline product.

[0003] A major environmental problem in the United States as well asother countries of the world is atmospheric pollution caused by theemission of combustion products from automobiles. Because of suchenvironmental considerations, refiners continuously strive to produceautomotive gasoline with reduced combustion emissions. It has now beenfound that combustion emissions from automotive gasoline can be reducedby the use of gasoline and gasoline blendstocks having a certaincomposition that provides a more hydrogen-rich fuel with enhanced energyvalue and reduced carbon dioxide emission than currently availablegasolines and blendstocks therefor. In particular, it has been foundthat diisopropylbenzene exhibits unique properties by providing energyfor doing work while producing fewer carbon dioxide emissions thancurrent gasoline blendstocks.

SUMMARY OF INVENTION

[0004] A relatively higher energy value unleaded gasoline fuel, suitablefor combustion in a spark ignition internal combustion engine and havingrelatively low undesirable emissions upon combustion, is produced byenriching the gasoline fuel with diisopropylbenzene. Thediisopropylbenzene enriched unleaded gasoline fuel of this inventioncontains at least 0.3 weight percent diisopropylbenzene, and preferablycontains about 0.3 to about 10 weight percent diisopropylbenzene.

[0005] Unleaded gasoline fuels embodying the present invention can beproduced utilizing aromatic blendstocks having aisopropylbenzene-to-diisopropylbenzene mole ratio in the range of about0 to 20. Typically, isopropylbenzene-to-diisopropylbenzene mole ratio inthe blendstock is in the range of about 1 to about 6.

BRIEF DESCRIPTION OF DRAWING

[0006] In the drawing,

[0007] The sole FIGURE is a flow diagram illustrating a process suitablefor the production of high-energy aromatic blendstocks for unleadedgasolines.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0008] A relatively high energy aromatic blendstock, containingdiisopropylbenzene and eminently well suited for making an unleadedgasoline fuel for combustion in an internal combustion engine with sparkignition can be produced as illustrated in the FIGURE. As shown in theflow diagram of the FIGURE, a light reformate from a naphtha reformerwhich contains benzene is charged to light reformate tower 10 wheremolecules containing five or six carbon atoms, for example isopentane,are removed and exit in an overhead C₅-stream 14 for further processingor blending. The light reformate preferably contains substantially noaromatic hydrocarbons other than benzene, toluene and xylene. Morepreferably, a relatively high concentration of benzene and toluene ispresent in the light reformate stream. The bottoms from light reformatetower 10 flow to light reformate tower 12 as stream 16. Distillation inlight reformates tower 12 separates benzene from toluene. Substantiallyall of the benzene in the light reformates feed goes into thebenzene-rich overhead products via overhead stream 18, along with otherreformate molecules boiling at about the same temperature. Substantiallyall of the toluene, along with other reformate molecules boiling atabout the same temperature as toluene, exit as the bottoms stream 20from tower 12. This heavy portion of light reformate may be purifiedfurther to produce industrial grade toluene for use as commercialsolvent or to make toluene diisocyanate (a precursor for polyurethanefoams), or it can be blended to gasoline as produced, or together withother components, as desired.

[0009] The benzene rich overhead stream 18 from tower 12 is combinedwith refinery grade propylene from stream 24 (usually a mixture of about30% propane and 70% propylene produced by other units such as a fluidcatalytic cracker) and charged to benzene conversion or aromaticalkylation's reactor 22 via stream 25. The feed to reactor 22 can alsobe relatively pure benzene and or relatively pure propylene. In thisreactor 22 benzene and propylene combine in the presence of an acidiccatalyst (solid phosphoric acid catalyst, zeolite catalyst, aluminumchloride catalyst, or the like) to form diisopropylbenzene, as well asisopropylbenzene and byproducts. The propane present in the refinerygrade propylene is separated from the relatively higher boiling reactoreffluent and is removed overhead as stream 26. The alkylation ofaromatics with propylene in the presence of an acidic catalyst, e.g. asolid phosphoric acid catalyst, is well known in the art and isdescribed, for example, in U.S. Pat. No. 5,792,894 to Huff, Jr. et al.

[0010] The alkylated aromatic product from the benzene conversionreactor 22 is then charged as stream 28 to distillation tower 30 forhigh-energy blendstock recovery. Light materials boiling below theboiling point of isopropyl benzene are recovered in the overhead stream32 of tower 30 and may be sent to gasoline blending. The bottoms stream34 from this tower has a relatively high diisopropylbenzene content andis charged to high-energy blendstock recovery tower 36, whereisopropylbenzene is recovered from the top of the tower 36 as stream 38,and diisopropylbenzene is recovered from the bottom of the tower asstream 40. These two high energy, low CO₂ emission generating productscan then be segregated and blended into gasoline products in desiredproportions. Alternatively, the bottoms stream 34 can be sufficientlyrich in diisopropylbenzene to be used directly as aromatic gasolineblendstock.

[0011] Gasoline fuels typically are composed of mixtures of aromatics,olefins and paraffins, and are produced by blending together severaldifferent, processed hydrocarbon streams, commonly referred to asblendstocks, into various grades of saleable products, e.g., unleadedregular and premium gasolines, each of which meets certain productspecifications. From an emissions standpoint, olefins are the leastdesirable gasoline fuel constituents, and olefin content preferably isminimized. More preferably, the produced gasoline fuel is substantiallyolefin-free.

[0012] For use in spark-ignition engines, most commercially availablegasoline fuels conform to the requirements of ASTM D4814-89specifications. Such gasolines fall into five different volatilityclasses as set forth in Table I below: TABLE I Gasoline SpecificationsProperties Class A Class B Class C Class D Class E RVP (psi) max 9.010.0 11.5 13.5 15.0 (atm) max 0.6 0.7 0.8 0.9 1.0 (kPa) max 62 69 80 93104 Dist. 10% (° F.) max 158 149 140 131 122 (° C.) max 70 65 60 55 50Dist. 50% (° F.) min-max 170-250 170-245 170-240 170-235 170-230 (° C.)min-max  77-121  77-118  77-116  77-113  77-110 Dist. 90% (° F.) max 374374 365 365 365 (° C.) max 190 190 185 185 185 End Point (° F.) max 437437 437 437 437 (° C.) max 225 225 225 225 225

[0013] To produce the aforementioned grades of gasoline, the blendstocksinclude n-butane, iso-butane, reformates, light hydrocrackate, heavyhydrocrackate, alkylates, aromatics, straight-run gasoline, straight-runnaphtha, cat-cracked gasoline and coker gasoline. The blend stocks areselected to produce a gasoline fuel with predetermined specifications toresearch octane number (RON), motor octane number (MON), and vaporpressure (usually specified as Reid Vapor Pressure or RVP).Diisopropylbenzene provides a convenient manner for adjusting the octanenumbers even in gasolines that have a relatively high paraffin ornaphthane content.

[0014] The blendstocks embodying the present invention contain alkylatedaromatics in which the aromatics content is at least 25 mole percent,the rest being constituted primarily by paraffin hydrocarbons, andpreferably having substantially no light (C₄ to C₆) olefin content. Thediisopropylbenzene content of the present aromatic blendstocks is atleast about 10 mole percent, preferably about 20 to about 30 molepercent, most preferably about 100 mole percent. Also, in the aromaticblendstocks of the present invention, the mole ratio ofisopropylbenzene(cumene)-to-diisopropylbenzene is a significantcharacteristic. This mole ratio in the present aromatic blendstocks isin the range of about 0 to about 20, and preferably in the range ofabout 1 to about 6.

[0015] The foregoing, aromatic blendstocks preferably have a relativelylow benzene content, and are incorporated into unleaded gasoline fuelsin an amount sufficient to provide a diisopropylbenzene content thereinof at least about 0.3 weight percent, preferably about 0.3 to about 10weight percent. The so constituted gasoline fuel preferably contains nomore than about 1 weight percent, preferably no more than about 0.5weight percent of benzene. The 90% distillation endpoint (T₉₀ max.)preferably is no more than about 375□ F. (190□ C.), and the Reid VaporPressure is no more than about 1 atmosphere (104 kPa), preferably about0.5 atmospheres (52 kPa) to about 0.9 atmospheres (93 kPa).

[0016] The benefits attainable with gasoline fuel compositions enrichedwith diisopropylbenzene are illustrated below. It will be noted thatdiisopropylbenzene provides added energy for doing work while producingsubstantially less carbon dioxide emissions than other comparablegasoline blendstocks.

[0017] The properties of common blendstock components, and ofdiisopropylbenzene, are compiled in Table II, below. TABLE II Propertiesof Blendstock Components Liquid Heat of Heat of Pounds Carbon DensityCombustion; Combustion; of CO₂ Weight Lbs/gal BTU per BTU per ProducedComponent RON % @ 60° F. Pound⁽²⁾ Gallon⁽²⁾ Per Gallon Benzene 104.992.3 7.361 17,258⁽³⁾ 127,036 24.9 Toluene 110.0 91.2 7.289 17,423⁽³⁾126,996 24.4 3-Ethylpentane 65.0 83.9 5.871 19,156⁽³⁾ 112,465 18.0Diisopropl 110.5 88.8 7.214 17,970⁽⁴⁾ 129,635 23.5 Benzene⁽¹⁾

[0018] Table III, below, illustrates the amounts of carbon dioxidegenerated by gasoline fuel blendstocks upon combustion. In theseblendstocks, a relatively high octane aromatic component is combinedwith a relatively low octane component to produce a mixture having thesame octane as a final target unleaded gasoline (92 Research OctaneNumber Unleaded Regular). 3-Ethylpentane is selected as a representativelow octane component, having seven carbon atoms and an octane typical ofthose in naphtha blendstocks. TABLE III Blendstock Examples Pounds Heatof BTU Volume of CO₂ Combustion, Percent Produced Produced RON In BlendPer Gallon Per Gallon Blend 1 Benzene 104.9  67.7 24.9 127,0363-Ethylpentane 65.0  32.3 18.0 112,465 Blend 92.0 100% 22.7 122,330Pounds of CO₂ per Million BTU delivered⁽⁵⁾: 186 Blend 2 DiisopropylBenzene 110.5  59.3 23.5 129,635 3-Ethylpentane 65.0  40.7 18.0 112,465Blend 92.0 100% 21.3 122,647 Pounds of CO₂ per Million BTU delivered⁽⁵⁾:174 Blend 3 Toluene 110.0  60.0 24.4 126,996 3-Ethylpentane 65.0  40.018.0 112,465 Blend 92.0 100% 21.8 121,184 Pounds of CO₂ per Million BTUdelivered⁽⁵⁾: 180${(5)\quad {Calculated}\quad {as}\quad {follows}\text{:}\quad {lbs}\quad {CO}_{2}} = \frac{( {{lbs}\quad {CO}_{2}\quad {per}\quad {gallon}} ) \times 10^{6}}{( {{BTU}\quad {per}\quad {gallon}} )}$

[0019] The RON values in Table III above are the volume weighted averageRON values of the individual components.

[0020] The superior benefits attainable by diisopropylbenzene byreducing CO₂ emissions are readily apparent. Whereas abenzene-containing blend is shown to emit 186 pounds of CO₂ per millionBTU delivered, the diisopropylbenzene-containing blend is shown to limitonly 174 pounds of CO₂ per million BTU delivered.

[0021] The total achievable benefit is even more striking when theUnited States' annual consumption of gasoline is considered. Thisbenefit is strikingly illustrated in Table IV below, if benzene ortoluene, respectively, is replaced by diisopropylbenzene. In both ofthese examples, the blend is selected to contain sufficient3-Ethylpentane to provide the target RON value of 92. Because arelatively larger volume of toluene-containing Blend 3 of Table III canbe replaced by the diisopropylbenzene containing Blend 2, asignificantly larger reduction in CO₂ emissions is achievable. TABLE IVAnnual CO₂ Reduction Benefit Replacing Benzene Item Value Comment UnitedStates gasoline consumption, gallons/day 306,900,000 EIA Publication;Average Year 1999 Benzene content of U.S. Gasoline pool 0.95% NIPERSurvey, Solomon Refining Survey Gallons of Benzene blended per day2,915,550 Gallons of Blend Number 1 blended per day 4,306,573 Gallons ofBenzene Divided by 67.7%⁽⁶⁾ Pounds of CO₂ Per Gallon of Blend 1 22.7Pounds of CO₂ Per Day Emitted via Blend 1 97,759,207 Gallons of Blend 1Times 22.7 BTU of Energy Per Day Obtained from Blend 1 526,823,075,090Gallons of Blend 1 Times 122,330 BTU of Energy Per Day Required fromBlend 2 526,823,075,090 Energy Content of Blend 2, BTU/Gallon 122,647From Table III, data for Blend 2 = Gallons Per Day of Blend 2 to DeliverEnergy 4,295,442 526,823,075,090/1 22,647 Pounds of CO₂ Per Gallon ofBlend 2 21.3 From Table Ill, data for Blend 2 = Pounds Per Day of CO₂Emitted by Blend 2 91,492,915 21.3 times 4,295,442 Pounds Per Day of CO₂Emitted by Blend 1 97,759,207 Pounds Per Day of CO₂ Emitted by Blend 291.492.915 Reduction in Pounds Per Day of CO₂ 6,266,292 Reduction inTons Per Year of CO₂ 1,143,598

[0022] TABLE V Annual CO₂ Reduction Benefit Replacing Toluene Item ValueComment United States gasoline consumption, gallons/day 306,900,000 EIAPublication; Average Year 1999⁽⁷⁾ Toluene to be replaced 7% Gallons ofToluene blended per day 21,483,000 Gallons of Blend Number 3 blended perday 35,805,000 Gallons of Toluene Divided by 600%⁽⁸⁾ Pounds of CO₂ PerGallon of Blend 3 21.8 Pounds of CO₂ Per Day Emitted via Blend 3780,549,000 Gallons of Blend 3 Times 21.8 BTU of Energy Per Day Obtainedfrom Blend 3 4,338,993,120,000 Gallons of Blend 3 Times 121,184 BTU ofEnergy Per Day Required from Blend 2 4,338,993,120,000 Energy Content ofBlend 2, BTU/Gallon 122,647 From Table III, data for Blend 2 Gallons PerDay of Blend 2 to Deliver Energy 35,377,899 =4,338,993,120,000/1 22,647Pounds of C02 Per Gallon of Blend 2 21.3 From Table III, data for Blend2 Pounds Per Day of CO₂ Emitted by Blend 2 753,549,249 =21.3 times35,777,899 Pounds Per Day of CO₂ Emitted by Blend 3 780,549,000 PoundsPer Day of CO₂ Emitted by Blend 2 753.549.249 Reduction in Pounds PerDay of CO₂ 26,999,751 Reduction in Tons Per Year of CO₂ 4,927,455

[0023] The foregoing specification and the examples therein areillustrative of the present invention, are not to be taken as limiting.Still other variants within the spirit and scope of the presentinvention are possible and will readily present themselves to thoseskilled in the art.

That which is claimed is:
 1. An unleaded gasoline fuel suitable forcombustion in a spark ignition internal combustion engine and containingat least about 0.3 weight percent diisopropylbenzene.
 2. The unleadedgasoline fuel in accordance with claim 1 containing about 0.3 to about10 weight percent diisopropylbenzene.
 3. The unleaded gasoline fuel inaccordance with claim 1, containing no more than about 1 weight percentbenzene.
 4. The unleaded gasoline fuel in accordance with claim 1,containing no more than about 0.5 weight percent benzene.
 5. Theunleaded gasoline fuel in accordance with claim 1 and substantially freefrom olefins.
 6. The unleaded gasoline fuel in accordance with claim 1and having a Reid Vapor Pressure no greater than about 1 atmosphere. 7.The unleaded gasoline fuel in accordance with claim 1 and having a ReidVapor Pressure of about 0.5 atmospheres to about 0.9 atmospheres.
 8. Theunleaded gasoline fuel in accordance with claim 1 and having a ReidVapor Pressure no greater than about 1 atmosphere and a 90% D-86Distillation Point no greater than about 375□ F.
 9. An aromaticblendstock, suitable for making an unleaded gasoline fuel for combustionin a spark ignition internal combustion engine and comprisingisopropylbenzene and diisopropylbenzene in aisopropylbenzene-to-diisopropylbenzene mole ratio in the range of about0 to about
 20. 10. The aromatic blendstock in accordance with claim 9wherein the isopropylbenzene-to-diisopropylbenzene mole ratio is in therange of about 1 to about 6.